Project summary Burden of acute respiratory infections (ARI) and associated viral respiratory pathogens is not well documented in India. Previous studies have identified respiratory syncytial virus (RSV) and influenza as among the common viruses involved in respiratory infection. Vaccination is among most effective strategies for prevention of influenza virus infection and its severe complications. However there are economic, operational as well as attitudinal barriers for adoption of Influenza vaccination. This calls for an evidence based concerted advocacy which is in keeping with the disease burden and epidemiology of influenza in India. Therefore, this project tries to assess the burden of ARI and associated respiratory pathogens among elderly population, and attempts to uncover excess influenza related mortality in India using modeling techniques. It also seeks to assess attitude of priority populations viz. elderly individuals and health care workers regarding influenza vaccination at multiple sites in different regions of the country. Such an approach towards introduction of vaccine for priority populations especially elderly is most likely to succeed. A community cohort of elderly (over 60 year) population will be recruited from four sites from different regions of the country for a two-year follow-up. By way of weekly visits, information on incident cases of ARIs will be collected. ARI cases will be classified into acute upper (AURI) or lower respiratory infection (ALRI). Naso- and oro-pharyngeal swabs will be collected from all cases of ALRI and a sub-sample of AURI, and age and sex matched neighborhood controls for testing for influenza and other respiratory viral pathogens. Incidence of ARI, both total and pathogen specific, as well as outpatient visit and hospitalization rates will be estimated from the cohort. Direct and indirect cost of influenza related respiratory illness will be ascertained from patients recruited from identified hospitals. Modeling techniques using virological and mortality data at national level will be used to generate estimates for influenza related mortality. One fifty to two hundred healthcare workers from the hospitals recruited for earlier study and 250 subjects from elderly cohort from each site will be recruited to assess their attitude and practices regarding influenza vaccination using standardized questionnaire.